1. Fifteen years ago the average weight of American men between the ages of 30 and 50 was µ = 166 pounds. A researcher would like to determine whether there has been any change in this figure during the past 15 years. A sample of n = 100 men is obtained. The average weight for this sample is = 173 with s = 23. On the basis of these data, can the researcher conclude that there has been a significant change in weight? Use a two-tailed test with α = 0.01.
2. A researcher would like to examine the effects of humidity on eating behavior. It is known that laboratory rats normally eat an average of µ = 21 grams of food each day. The researcher selects a random sample of n = 100 rats and places them in a controlled-atmosphere room where the relative humidity is maintained at 90%. The daily food consumption for the sample averages = 18.7 with SS = 2475. a. On the basis of this sample, can the researcher conclude that humidity affects eating behavior? Use a two-tailed test with a = .05.
3. A psychologist would like to determine whether there is a relation between depression and aging. It is known that the general population averages µ = 40 on a standardized depression test. The psychologist obtains a sample of n = 36 individuals who are all older than age 70. The average depression score for this sample is = 44.5 with SS = 5040. On the basis of this sample, can the psychologist conclude that depression for elderly people is significantly different from depression in the general population? Test at the .05 level of significance.
4. A fund raiser for a charitable organization has set a goal of averaging at least $25 per donation. To see if the goal is being met, a random sample of recent donations is selected. The data for this sample are as follows: 20, 50, 30, 25, 15, 20, 40, 50, 10, and 20. Use a one-tailed test with a = .05 to determine whether the donations are averaging significantly greater than $25.